Rigid crankshaft cradle and actuator

ABSTRACT

Crankshaft main bearing failure in variable compression ratio engines having eccentric main bearing supports is prevented by rigidly supporting the bearings in a crankshaft cradle. The crankshaft cradle is rotatably mounted in the engine on a first axis, and the crankshaft is mounted in the crankshaft cradle on a second axis off-set from the first axis. The crankshaft cradle comprises eccentric members that support the bearing elements, and structural webbing that rigidly hold the eccentric members in alignment with one another at all times. Bearing caps and fasteners rigidly and removably secure the crankshaft in the crankshaft cradle. An actuator rotates the crankshaft cradle and adjusts the position of the crankshaft axis of rotation and the compression ratio of the engine. The crankshaft cradle rigidly holds the main bearings in precise alignment at all times and provides long bearing life.

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for adjustingthe compression ratio of internal combustion engines, and morespecifically to a method and apparatus for adjusting the position of thecrankshaft with eccentric crankshaft main bearing supports.

Designs for engines having eccentric crankshaft main bearing supportshave been known for sometime. In these engines the eccentric mainbearings are rotated to adjust the position of the crankshaft's axis ofrotation. Poor rotational alignment of the eccentric main bearingsupports is a problem for these engines because even small amounts ofmain bearing misalignment can cause rapid main bearing failure.

Significant forces bear down on the eccentric main bearing supportsduring operation of the engine. In modern passenger car engines mainbearing loads can exceed 50 MPa. The forces exerted on the eccentricmain bearing supports are at times significantly different from oneeccentric main bearing support to the next. For example, inmulti-cylinder engines a clockwise torque may be applied on a firsteccentric main bearing support from the combustion pressure bearing downon the first piston, connecting rod and crank throw, and acounterclockwise torque may be applied on a second or third eccentricmain bearing support from the inertial forces of the second piston andconnecting rod pulling up on the second crank throw. As a secondexample, in a single cylinder engine having two eccentric main bearingsupports the torque applied to the crank throw and the resistive torqueat the power take off end of the crankshaft cause uneven loading on theeccentric main bearing supports. These large unequal forces are aproblem because they cause the eccentric sections to rotate out ofalignment with one another causing rapid failure of the crankshaft mainbearings.

In U.S. Pat. No. 887,633, and in German patent DE 3644721 A1 a pinnedlinkage is show for adjusting the rotational alignment of the eccentricmain bearing sections. U.S. Pat. No. 4,738,230 shows dowels extendingfrom each eccentric main bearing support that are fitted into slotslocated in a slidable bar for adjusting the rotational alignment of theeccentric main bearing supports. U.S. Pat. Nos. 5,572,959 and 5,605,120show gear teeth extending from eccentric main bearing supports thatengage a layshaft with mating gears for adjusting the rotationalalignment of the eccentric main bearing supports. U.S. Pat. No.1,160,940 shows a bail shaped frame that connects adjacent eccentricsections for adjusting the rotational alignment of the eccentricsections. Poor alignment of the main bearings is a significant problemfor each of these systems. In addition to poor main bearing alignment anumber of these systems are not mechanically functional for otherreasons, are impractical for mass production manufacture and assembly,and/or are not functional for engines having more than two mainbearings. For example, U.S. Pat. No. 1,160,940 shows a bail shaped framethat is weakly connected to the eccentrics and that does not have arigid construction. In addition to not rigidly hold the bearings inalignment. the system is not mechanically functional because theconnecting rod does not clear the bail shaped frame. The system is alsonot functional for engines having more than two main bearings because itis not possible to slide the eccentric main bearing support onto thecenter crankshaft journal or journals.

A further problem with engines having rotatable eccentric main bearingsupports in a fixed engine housing is that the location of thecrankshaft rotational axis changes with change of compression ratio,making use of a conventional in-line clutch impossible. Geared powertake-off couplings for engines having an adjustable crankshaftrotational axis are shown in the prior art, however a problem with thesesystems is that heavy structural reinforcing is required to rigidly holdthe gear set in alignment. In addition to the problem of added weight,engine housing length is also increased.

German patent DE 3644721 A1 shows a gear set mounted to the free end ofone of the eccentric crankshaft main bearing supports. The gear set hasan intermediary shaft and an output shaft. The output shaft pointsgenerally away from the crankshaft, and has a fixed axis of rotation forall compression ration settings. A problem with the system shown inGerman patent DE 3644721 A1 is that during periods of high engine torquethe end eccentric main bearing support may bend out of alignment,resulting in damage to the crankshaft main bearing. The gear set is alsobulky and increases cranktrain friction losses due to the increasednumber of bearings and gear friction. U.S. Pat. No. 4,738.230 shows afirst spur gear mounted on the crankshaft and a second spur gear havingan axis of rotation that is concentric with the axis of rotation of themain bearing supports. These gears are too small to carry the torsionalloads of the engine. U.S. Pat. No. 4,738,230 also shows a power take-offsystem having an internal or annular gear set. Heavy and lengthystructural reinforcing is required for holding the ring gear shaft inrigid alignment with the gear mounted on the end of the crankshaft. U.S.Pat. Nos. 5,443,043, 5,572,959 and 5,605,120 show a crankshaft having afixed axis of rotation and an upper engine that changes positionrelative to its supporting frame when the compression ratio is changed.While a conventional in-line clutch can be employed with thisarrangement, the position of the upper engine is changed when thecompression ratio is changed, and the inertial mass of the upper engineprevents rapid adjustment of compression ratio.

SUMMARY OF THE INVENTION

In the present invention, a rotatable rigid crankshaft cradle isemployed for holding the crankshaft main bearings in alignment. Thecrankshaft cradle is rotatably mounted in the engine on a pivot axis,and the crankshaft is mounted in the crankshaft cradle on a second axisoff-set from the pivot axis. An actuator rotates the crankshaft cradleand adjusts the position of the crankshaft axis of rotation and thecompression ratio of the engine. The crankshaft cradle rigidly holds themain bearings in precise alignment at all times and provides longbearing life. The crankshaft cradle provides rigid support ofcrankshafts for single and multi-cylinder engines, ranging fromcrankshafts having two main bearings for single and two cylinderengines, to crankshafts having five or more main bearings forin-line-four cylinder engines, V8 engines, as well as other engines. Inaddition to providing a long main bearing life, the variable compressionratio mechanism of the present invention is reliable and has a low cost.

Referring now to FIGS. 3, 4 and 5, in the preferred embodiment of thepresent invention a crankshaft cradle 60 is rotatably mounted in theengine housing on a pivot axis E, and a crankshaft 61 is mounted in thecrankshaft cradle on a second axis A off-set from the pivot axis. Thecradle includes two or more main bearing supports or eccentric members62 and structural webbing 64 for rigidly holding the eccentric membersand main bearings in alignment. One or more bearing caps 68 are fastenedto the cradle with bolts or another type of fastener for securing thecrankshaft in the cradle. The bearing caps are removable from the cradlepermitting assembly of the crankshaft in the cradle. Operation of themain bearings without failure requires precise alignment of the mainbearing supports at all times. According to the present invention,adjacent main bearing supports are held in rigid alignment at all timesby structural webbing 64. More specifically. the structural webbingholds the main bearing supports in rigid alignment at all timesproviding a long service life for the main bearings.

FIG. 9 shows a second embodiment of the present invention. As shown inFIG. 9, crankshaft cradle 146 includes a first eccentric member, or mainbearing support 160 and a second eccentric member, or main bearingsupport 162. The crankshaft cradle is assembled by sliding main bearingsupport 160 over a first end of crankshaft 152, and sliding the secondmain bearing support 162 over the second end of crankshaft 152 andrigidly fastening the main bearing supports together with one or morebolts 164. The main bearing supports include structural webbing forrigid attachment of the first main bearing support to the second mainbearing support. The crankshaft applies large loads on main bearings 12,and the assembled crankshaft cradle 146 holds main bearings 12 inprecise alignment under the high load conditions and more generallycrankshaft cradle 146 holds main bearings 12 in precise alignment at alltimes.

An actuator first adjusts the rotational position of the crankshaftcradle about its pivot axis, and then locks the rotational position ofthe cradle in place. The actuator applies force on the cradle at acentral location between the main bearings, and more generally betweenthe front and back eccentric members, whereby twisting of the crankshaftcradle and miss alignment of the main bearings is minimized.Accordingly, the eccentric members are rigidly maintained in alignmentproviding a long main bearing life. Another advantage of the presentinvention is that the cradle has a small inertial mass, and the actuatorcan adjust compression ratio settings rapidly.

Power is transferred from the crankshaft to the power take-off shaftthrough gears 14 and 18. According to the present invention, gears 14and 18 have a variable centerline distance and a variable backlashvalue. According to the present invention, the power take-off shaft ispositioned to provide a small maximum gear backlash value for a largechange in compression ratio. The power take-off coupling of the presentinvention provides long gear life exceptional reliability, low noiselevels, and a low cost.

According to the present invention, the power takeoff shaft is locatedwithin ±45° of an imaginary first plane and preferably within ±33°. Thefirst plane passes through the crankshaft cradle pivot axis E and isperpendicular to the translation axis or centerline axis of thepiston(s), providing a small change in backlash from one compressionratio setting to the next. More specifically, location of the powershaft within ±45° of the first plane, and preferably within +33°,provides a small gear backlash, low gear noise, and long gear life.Additionally, gears 14 and 18 are mounted on parallel shafts andpreferably have helical involute teeth permitting operation of the gearswith small variations in centerline distance. Gears 14 and 18 are ofautomotive quality and have a diameter and width that provides a longgear life.

Prolonged operation of gears 14 and 18 without failure requiresmaintenance of parallel alignment of gear 14 and gear 18. According tothe present invention, the crankshaft cradle holds the bearing elementsthe crankshaft, and gear 14 in precise parallel alignment at all timeswith the power take-off shaft and gear 18. According to the presentinvention, high structural loads are applied by the crankshaft on thebearing elements, and the crankshaft cradle rigidly holds the mainbearing supports in precise parallel alignment at all times preventingfailure of the bearing elements and preventing failure of gears 16 and18.

The power take-off shaft is located adjacent to crankshaft cradle in theengine housing, and is rigidly supported with only a minimal increase ofengine size and weight. A further advantage of the present invention isthat the power take-off shaft may also serves as a balance shaft. FIG. 9shows an embodiment of the present invention where the power take-offshaft also serves as a balance shaft for the engine. The engine shown inFIG. 9 has a small size and low bearing and gear friction in partbecause balancing and power take-off is accomplished with a singleshaft.

Referring now to FIGS. 3, 4, 5 and 9, gear 14 mounted on the crankshafttransfers power from the crankshaft to a second gear 18 mounted on thepower take-off shaft mounted in the engine housing. The crankshaftrotates on axis A and the power take-off shaft rotates on axis P Axis Aand axis P are separated by a centerline distance. According to thepresent invention, rotation of the crankshaft cradle on the pivot axis Eadjusts the position of the crankshaft, adjusts the compression ratio ofthe engine, and changes the centerline distance between axis A and axisP, causing the backlash clearance between gear 14 and gear 18 to change.According to the present invention, a small maximum gear backlash valueis provided by locating the axis of rotation of gear 18 on or near aplane that passes through the axis of rotation of the crankshaft andthat is generally perpendicular to the line of translation or centerlineof the first piston(s).

The power take-off arrangement according to the present invention issignificantly smaller, lighter, and less costly than prior art systemsfor engines having eccentric main bearing supports. Additionally, thepresent invention provides a low friction, compact, and light weightcombined balance shaft and power takeoff gear set. The variablecompression ratio mechanism according to the present invention holds thecrankshaft main bearings in rigid alignment and provides a long bearinglife. More specifically, the rigidity of the crankshaft cradle holds thebearings in alignment and prevents damage caused by bearing misalignmentand vibration. The present invention is reliable and durable. Thepresent invention can be manufactured using standard materials andmass-production methods, and has a low cost. Another advantage of thepresent invention is that the main bearings can be line bored, accordingto current manufacturing practices, to establish precise main bearingalignment. The variable compression ratio mechanism has a small inertialmass and a fast response providing rapid change of compression ratio.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a section of the variable compression ratio engineaccording to the present invention. FIG. 1 also shows sectional viewF1—F1 of FIG. 2.

FIG. 2 shows sectional view F2—F2 of FIG. 1. FIG. 2 shows thecrankshaft, cradle, power shaft, and power output coupling.

FIG. 3 shows a three cylinder engine according to the present invention.

FIG. 4 shows a detailed view of the crankshaft cradle, shown in FIG. 3.

FIG. 5 shows a partial sectional view F5—F5 of FIG. 1.

FIG. 6 is a detailed view of fluid chamber 72 shown in FIGS. 1 and 2.

FIG. 7 is similar to FIG. 1 but shows a two cylinder engine having oilchamber 108, oil chamber 110, and crankshaft cradle 112.

FIG. 8 shows a partial sectional view of an engine according to thepresent invention.

FIG. 9 shows a partial sectional view of an engine according to thepresent invention. FIG. 9 also shows a partial sectional view of engine136 taken along cut lines F9—F9 shown in FIG. 8.

FIG. 10 shows a partial sectional view of an engine according to thepresent invention having a first actuator having a connecting arm and asecond actuator having a connecting arm, for adjusting and retaining theposition of the crankshaft cradle.

FIG. 11 is similar to FIG. 3 and shows another embodiment of the presentinvention.

FIG. 12 shows a partial section of an engine according to the presentinvention having a close spacing between the crankshaft and the powershaft.

RIGID CRANKSHAFT CRADLE AND ACTUATOR

FIGS. 1 and 2 show a portion of a variable compression ratio engine 2according to the present invention. Engine 2 has a piston 4, aconnecting rod 6, a crankshaft 8 having a crankshaft rotational axis Aand having one or more crank throws or cranks 10 having a crank throwcenterline B, crankshaft main bearings 12, a crankshaft power take-offgear or output gear 14, a power shaft 16 having a power shaft rotationalaxis P preferably parallel to crankshaft axis A, a power input gear orpower shaft gear 18, a cylinder 20 having cooling means such as a waterjacket 22, a housing 24, a cylinder head 26, one or more intake valves28, one or more exhaust valves 30, fuel injection or carburetion means32, and one or more spark plugs 34. Crank 10 has a stroke 2L equal totwice the distance from axis A to axis B. Crankshaft 8 is rotatablymounted in a ridged crankshaft cradle 36 having one or more eccentricssuch as eccentrics 38 and 40. According to the present invention, engine2 includes an actuator 42 (shown in FIG. 6) for adjusting the rotationalposition of a crankshaft cradle 36 on a crankshaft cradle axis or pivotaxis E, and for adjusting the position of crankshaft rotational axis Arelative to housing 24. More specifically, the cradle is mounted in theengine for pivoting relative to the engine about the pivot axis, thepivot axis is preferably substantially parallel to and spaced from therotational axis of the crankshaft, and the actuator varies the positionof the cradle about the pivot axis, and adjusts the compression ratio ofthe engine. According to the present invention actuator 42 may be ahydraulic actuator, an electromechanical actuator. a rotary actuator, astraight hydraulic cylinder actuator, or another type of actuator.Preferably, engine 2 is a four-stroke port fuel injected spark-ignitionengine. Those skilled in the art will appreciate that according to thepresent invention engine 2 may be a direct fuel injection spark-ignitionengine, a diesel engine, a two-stroke engine, or another type ofreciprocating piston engine or variable volume machine such as aStirling engine, a steam engine, a pump, a compressor, or an expander(all not shown), and that other effective arrangements of valving, fuelsupply and ignition means may be provided and/or omitted. Those skilledin the art will appreciate that housing 24 and cylinder head 26 may beseparable, a single cast part, or other functional arrangement. Piston 4is slidably housed in cylinder 20 which is provided air through intakevalve 28. Intake valve 28 may include an adjustable valve actuationmechanism 44.

Engine 2 has one or more cylinders 20. In multi-cylinder enginesaccording to the present invention, the cylinders are preferably in-lineor in a steep “V” orientation, as shown in FIG. 7, however otherarrangements may be used. Referring now to the single cylinder shown inFIGS. 1 and 2, within engine 2 the geometric cylinder displacement D ofthe cylinder within engine 2 is equal to the product of the full strokeof piston 4 in cylinder 20 times the cross sectional area of cylinderbore 20. The engine displacement or cylinder displacement of enginesaccording to the present invention having one or more cylinders is thesum of the geometric cylinder displacements of all of the workingcylinders of the engine. Imaginary point X is located at the geometriccenter of the cross sectional area of cylinder bore 20, and immediatelyabove (just out of reach of) piston 4 when piston 4 is fully extendedaway from crankshaft rotational axis A when engine 2 is at its highestcompression ratio setting. Preferably, cylinder bore 20 is round,however cylinder bore 20 may have other cross sectional area shapes suchas oval, square, or another shape. Those skilled in the art willappreciate that the top of piston 4 may be flat or have a non-flatsurface. The cylinder within engine 2 has a combustion chamber volume,or end chamber volume, d having a minimum d_(min) and a maximum d_(max).Combustion chamber volume d is the volume between cylinder head 26 andpiston 4 when piston 4 is fully extended away from crankshaft rotationalaxis A. Crankshaft rotational axis A has a first position located on anaxis F that provides the smallest combustion chamber volume, d_(min).Combustion chamber volume d_(min) is the volume between cylinder head 26and piston 4 when piston 4 is fully extended away from crankshaftrotational axis A and crankshaft rotational axis A is located on axis F(e.g., rotational axis A is at its closest position to imaginary pointX). Crankshaft rotational axis A has a second position located on anaxis G that provides the largest combustion chamber volume, d_(max).Combustion chamber volume d_(max) is the volume between cylinder head 26and piston 4 when piston 4 is fully extended away from crankshaftrotational axis A and crankshaft rotational axis A is located on axis G(e.g., rotational axis A is at its farthest position from imaginarypoint X). The compression ratio C of the cylinder shown within engine 2is equal to,

C=(D+d)/d

The maximum compression ratio C_(max) of the cylinder shown withinengine 2 is equal to,

C _(max)=(D+d _(max))/d _(min)

The minimum compression ratio C_(min) of the cylinder shown withinengine 2 is equal to,

C _(min)=(D+d _(max))/d _(max)

Crankshaft cradle 36 is rotatably mounted in a bore 46 in housing 24.Crankshaft cradle 36 may have a first eccentric member, main bearingsupport or section 48 and a second eccentric member, main bearingsupport or section 50. Crankshaft cradle 36 has one or more eccentricssuch as eccentrics 38 and 40. Eccentric 38 is formed in section 48 andeccentric 40 is formed in section 50. Section 48 includes webbing 52,and section 50 includes webbing 54. Webbing 52 and 54 rigidly connectseccentric members 48 and 50 to one another. In detail, eccentrics 38 and40 are rigidly joined by webbing 52 and 54, and may be held in positionby a fastener such as pin, clip, screw or bolt 56 and more generallyeccentric member sections 48 and 50 are rigidly, and preferablyremovably, connected together with one or more fasteners.

Referring now to FIGS. 3, 4 and 5, in the preferred embodiment of thepresent invention, crankshaft cradle 60 has eccentric members orsections 62. Adjacent eccentric members or sections 62 are rigidlyjoined by webbing 64. Adjacent eccentric members or sections 62 joinedby webbing may be an single cast part (as shown), or may be an assemblyof parts, and more specifically crankshaft cradles comprising two ormore eccentric members 62 and webbing 64 may be a one-piece cast part oran assembly of parts. FIGS. 4 and 5 show four eccentric members 62 andwebbing 64 cast together as one rigid part and supporting four mainbearings 66. Sections 68 may serve as crankshaft main bearing caps.Bearing cap bolts or fasteners 70 rigidly and preferably removablysecure said bearing caps 68 to eccentric member or sections 62.Referring now to FIGS. 1 through 5, according to the present invention,adjacent eccentric members are rigidly joined by webbing effective forrigidly holding the eccentric members and the crankshaft main bearingsin alignment on crankshaft centerline axis A.

Referring to FIGS. 1 and 2, main bearings 12 are mounted or formed ineccentrics 38 and 40 for supporting crankshaft 8. Bearings 12 may bejournal bearings. roller, needle, tapered, spherical, or ball bearings,or any other functional bearing means for supporting crankshaft 8 ineccentric 38 and 40. Preferably bearings 12 are separable permittingassembly of crankshaft 8 in crankshaft cradle 36. Bearings 12 may beseparable by sliding sections 48 and 50 apart along axis E. Referringnow to FIGS. 3, 4 and 5, bearings 66 are separable by removing bolts 70and separating eccentric member or section 62 and bearing cap or section68.

Referring now to FIGS. 1 and 2, crankshaft cradle 36 and eccentrics 38and 40 rotate about a pivot axis E. According to the present invention,one or more fluid chambers 72 are formed between housing 24 (and/orhousing 24 plus one or more end surfaces 74 and 76) and crankshaftcradle 36. Those skilled in the art will appreciate that other surfacesmay be used to contain fluid within chamber 72. The fluid in chamber 72is oil or a similar hydraulic working fluid. The rotational position ofcrankshaft cradle 36 and eccentrics 38 and 40 on pivot axis E isadjusted by adjusting the volume of chamber 72. Preferably, the fluid inchamber 72 exerts a force directly on crankshaft cradle 36, causingcrankshaft cradle 36 to rotate about pivot axis E, and causing theposition of crankshaft rotational axis A to be adjusted. The volume ofchamber 72 is adjusted by admitting or releasing fluid from chamber 72,and in more detail by pumping fluid into chamber 72 or releasing fluidfrom chamber 72. Chamber 72 is in fluid communication with one or morefluid passageways 78. One or more valves 80 control flow of fluidthrough passageway 78 (or other passageway in fluid communication withchamber 72), and thus control flow of fluid into and out of chamber 72.Valve 80 is controlled by a controller 82 or other control means.Crankshaft cradle 36 and eccentrics 38 and 40 may rotate up to 0 degreesfrom a first position to a second position. In the first position,crankshaft rotational axis A is located on axis F, and in the secondposition crankshaft rotational axis A is located on axis G. Referringnow to the combustion chamber volume d shown within engine 2, releasingfluid from chamber 72 through valve 80 causes crankshaft cradle 36 torotate (clockwise) about pivot axis E θ degrees (due to downward. forceon eccentric sections 38 and 40, and on crankshaft cradle 36 fromcrankshaft 8 and/or due to other applied forces), causing crankshaft 8to move (be lowered) from centerline F to centerline G, causing volume dto be increased from d_(min) to d_(max) and causing the compressionratio C of the cylinder shown within engine 2 to be reduced from C_(max)to C_(min.)Fluid can be pumped back into the chamber 72 to rotatecrankshaft cradle 36 counterclockwise, causing the compression ratio Cto be increased. Those skilled in the art will appreciate that thecrankshaft rotational axis A can be adjusted to any position betweenaxis F and axis G, and compression ratio C can be adjusted to any valuebetween C_(max) and C_(min). According to the present invention, thevolume of chamber 72 is adjusted to adjust the rotational position ofcrankshaft cradle 36 and eccentrics 38 and 40. Adjusting the rotationalposition of crankshaft cradle 36 and eccentrics 38 and 40 adjusts theposition of crankshaft rotational axis A (e.g., the rotationalcenterline position of crankshaft 8) relative to housing 24, and adjuststhe compression ratio C of engine 2. Those skilled in the art willappreciate that engine 2 can have one or more cylinders, and that thecompression ratio C, displacement D, and combustion chamber volume d canbe the same or different for each of the cylinders according to thepresent invention.

FIG. 6 shows a detailed view of chamber 72, and more generally a rotaryactuator 42 for rotating crankshaft cradle 36 and eccentrics 38 and 40relative to housing 24. Referring now to FIGS. 1, 2 and 6, crankshaftcradle 36 has a surface 84 at radius R1 from pivot axis E that slidablyengages a first chamber end surface 86 extending from bore 46. Surface84 is preferably located on webbing 52 and 54. Those skilled in the artwill appreciate that surface 84 may touch end surface 86 or be separatedfrom end surface 86 by a small clearance (e.g., by a small workingtolerance between parts). Chamber 72 has a second chamber end surface 88extending from surface 84 that slidably engages bore surface 46. Thoseskilled in the art will appreciate that end surface 88 may touch bore46, or be separated from bore 46 by a small clearance (e.g., by a smallworking tolerance between parts). Chamber 72 is formed by surface 84,bore surface 46, end surface 88, end surface 86, and a top surface 74and a bottom surface 76. Those skilled in the art will appreciate thattop surface 74 and/or bottom surface 76 may be a continuation of, orradiused from. surface 46, surface 84, surface 88, and/or surface 86.

One or more seals may be used to retain fluid in chamber 72, such asface seals 94 and 96, line seals 98 and 100, and end surface seal 102and 104. Those skilled in the art will appreciate that other seal typesand arrangements may be used to retain fluid in chamber 72. According tothe present invention, hydraulic fluid in chamber 72 acts on crankshaftcradle 36. More generally, crankshaft 8 is mounted in eccentrics 38 and40 in crankshaft cradle 36, and crankshaft cradle 36 is the rotaryelement of rotary actuator 42, e.g., crankshaft 8 is mounted in therotary element of the rotary actuator. The present invention is compactin design and provides ridged support of crankshaft 8, which improvescrankshaft durability and life, and reduces vibration and noise. Thepresent invention is simple in design and inexpensive to manufacture,and has exceptional reliability and durability.

At times during operation of the present invention, the fluid in chamber72 is at high pressure, such as during the power stroke of engine 2 whenpiston 4 is bearing down on connecting rod 6. During the intake strokeof engine 2, the downward motion of piston 4 and connecting rod 6 maycause crankshaft 8 to exert an upwards force on eccentrics 38 and 40,causing crankshaft cradle 36 to rotate counterclockwise, and the fluidpressure in chamber 72 to decrease. Crankshaft cradle 36 may be held inposition by retaining means such as a pre-tensioning spring 106 (seeFIG. 9), a second hydraulic fluid chamber (see FIGS. 7, 10, and 12), afriction brake, a sliding pin, or other means that fixes orsubstantially retain and/or hold firm the position of crankshaft cradle36 relative to housing 24. Pre-tensioning spring 106 may be used toexert a clockwise torque on crankshaft cradle 36 (e.g., spring 106 movescrankshaft axis A in a direction generally away from piston 4,encouraging the compression ratio to be reduced), to minimize and/orprevent counterclockwise movement of crankshaft cradle 36 when a changeof compression ratio is not being sought. Spring 106 minimizes and/orsubstantially prevents rotational vibration or bounce of crankshaftcradle 36 in bore 46.

FIG. 7 is similar to FIG. 1 except that FIG. 7 shows a first fluidchamber 108, a second fluid chamber 110, a crankshaft cradle 112, andwebbing 111. Chamber 108 is similar to chamber 72 (shown in FIGS. 1 and6) in that increasing the volume in chamber 108 (e.g., by pumpinghydraulic fluid into chamber 108) rotates crankshaft cradle 112counterclockwise, causing crankshaft 8 to be raised and the compressionratio C to be increased. Chamber 110 is filled with fluid to retaincrankshaft cradle 112 in a fixed or near fixed position, and preventcrankshaft cradle 112 from substantively rotating or vibrating under thecyclic (and in some cases reversing) loads applied to crankshaft cradle112 by crankshaft 8, and in more detail to retain crankshaft cradle 112in a fixed or near fixed position except during periods when valves 114and/or 116 are adjusted to adjust the position of crankshaft cradle 112and main bearings 12 relative to housing 24. Chamber 110 may also beused to forcibly rotate crankshaft cradle 112 clockwise, causingcrankshaft 8 to be lowered, and causing the compression ratio C to belowered. Controller 82 and valves 114 and 116 are used to control feedof fluid into and out of chambers 108 and 110 through fluid passageways118 and 120. Other valves and fluid passageways, and other valve andfluid passageway arrangements may be used to control the volume of fluidin chambers 108 and 110.

Referring now to FIGS. 1 and 2, power is transferred from crankshaft 8to power take-off shaft 16 through a power output coupling 58 comprisinggears 14 and 18. According to the present invention, the distancebetween the crankshaft rotational axis A and the power shaft rotationalaxis P changes as the crankshaft rotational axis A is moved and thecompression ratio of the engine is changed. More specifically, the poweroutput coupling has at least one external power take-off gear 14 oncrankshaft 8 and power shaft 16 has an axis of rotation P and anexternal power input gear 18. External power take-off gear 14 is engagedwith external power input gear 18, and crankshaft 8 has a first axialposition having a first distance from power shaft axis P at a said firstpivot position of cradle 36, and crankshaft 8 has a second axialposition having a second distance from power shaft axis P at a secondpivot position of cradle 36. and the second distance is greater thansaid first distance. Gears 14 and 18 are external gears (not internal orannular gears) and have involute, epicycloid or other suitable geartooth shapes so that the durability of the gears is not substantivelyeffected by minor changes in the centerline distance between thecrankshaft 8 and the power shaft 16. Preferably gears 14 and 18 arehelical gears having parallel axes of rotation, to provide a higher loadcarrying capacity, a higher operational speed capability, and reducednoise.

Referring now to FIGS. 1 and 7, each piston 4 in the engine has atranslation axis 91. Engines according to the present invention have amean translation axis or centerline axis 92, where the centerline axis92 is defined as the translation axis 91 in single cylinder engines andthe bisecting or average translation axis in multi-cylinder V or Wengines.

In order to minimize change in the distance between the crankshaft gear14 and the power shaft gear 18 during changes of compression ratio, inthe preferred embodiment, axis P is positioned within plus or minus 45°of a first plane. Specifically, a first plane 90 passes through pivotaxis E and is perpendicular to the centerline axis 92. A firstcrankshaft axis is located approximately on the first plane, saidcenterline axis and said crankshaft axis being on the same side of saidpivot axis. A second plane 90 b passes through the first crankshaftaxis, said second plane and said first plane being separated by 45°, anda third plane 90 c passing through said first crankshaft axis, saidthird plane and said first plane being separated by 45° and said secondplane and said third plane being separated by 90°. Axis P is locatedbetween the second plane and the third plane, thereby minimizing themaximum backlash between the external power take-off gear and theexternal power input gear. Those skilled in the art will appreciate thataxis P may be located to the right or left of crankshaft 8 according tothe present invention. Alternatively, the first plane has its origin atand is perpendicular to, a second plane that passes through axis F andG. Axis P is positioned within plus or minus 45° of the first plane,where the plus or minus 45° is measured from the origin of the firstplane. Those skilled in the art will also appreciate that placement ofaxis P within plus or minus 45° of the first plane provides a minimumgear backlash in engines both having rigidly connected and not rigidlyconnected main bearing supports.

An anti-backlash gear 112 may be used to prevent gear chatter and wear.Anti-backlash gear 112 is spring loaded to keep the larger load bearinggear 18 in contact with its mating crankshaft gear 14 at all or almostall times. Alternatively, an anti-backlash gear may be mounted oncrankshaft 8. Power shaft 16 may have one or more balance weights 124.Those skilled in the art will appreciate that the balance weight 124 isoptional. In the preferred embodiment, the power output of the engine isthrough the power shaft, since its centerline is fixed along axis P, andthus power shaft 16 can easily be coupled to a clutch, transmission orother rotating element (all not shown). Power output for boats,airplanes, and some other applications may be directly throughcrankshaft 8, as adjusting the centerline of crankshaft 8 may notsignificantly affect system performance.

Referring now to FIGS. 1, 2, and 6, preferably the engine is assembledby sliding crankshaft cradle 36 into bore 46 along axis E. Bore 46 inhousing 24 can be machined at low cost and provides ridged support ofcrankshaft cradle 36. One or more parts 126 may be attached (or formedinto the inside of bore 46) by a screw 128 or other attachment meanssuch as a bolt, a slot, or adhesive. Those skilled in the art willappreciate that other parts may be attached or formed into the inside ofbore 46. Attaching parts inside bore 46 (as opposed to machining formsextending inward from radius R2) enables bore 46 to be machined at lowcost. An opening 130 (dashed lines) may be provided for access to boltsand for oil drainage.

A significant advantage of the present invention is that crankshaftcradle 36 and housing 24 rigidly hold crankshaft main bearings 12 inalignment (for single and multi-cylinder engines). Rigidly supportingthe crankshaft main bearings 12 in alignment significantly improvescrankshaft durability, and reduces noise and vibration. Those skilled inthe art will appreciate that a crankshaft for a multi-cylinder/pistonengine can be rigidly supported with the present invention, and forexample with an eccentric that has more than two ridged crankshaftbearing supports.

In the single cylinder engine shown in FIGS. 1 and 2, crankshaft cradlesections 48 and 50 slide onto the ends of the crankshaft 8, and may alsoslide into bore 46. The crankshaft cradle sections 48 and 50 may befastened together by a screw 56 or by other fastener means such as abolt, pin, brazing, or adhesive. Preferably, end plates 132 and 134 arebolted to housing 24 to secure crankshaft cradle sections 48 and 50 inplace. Endplates 132 and 134 may be used to retain crankshaft cradlesections 48 and 50 in position. Bolting endplates 132 and 134 to housing24 may compressively set seals 102 and 104 in place. Those skilled inthe art will appreciate that one or both endplates may be formed inhousing 24 (for example, one or both end surfaces 76 and 74, may bemachined out of housing 24), and/or other means may be used to retaincrankshaft cradle sections 48 and 50 in position.

FIG. 11 shows in sectional view part of a three cylinder variablecompression ratio engine according to the present invention, having apiston 4, a connecting rod 6, a crankshaft 61 having a rotational axis Aand crankshaft bearings 66, a cylinder 20, in a housing 59, ancrankshaft cradle 60, and an eccentric main cap 71. Crankshaft cradle 60comprises eccentric members or section 62 and webbing 64 rigidlyconnecting two or more of the eccentric members 62. Eccentric members 62and bearing caps or sections 68 have a separation surface 63. Thoseskilled in the art will appreciate that separation surface 63 may be onan imaginary flat plane that bisects axis A, a curved surface thatbisects axis A, or another imaginary surface that allows assembly ofcrankshaft 61 into crankshaft cradle 60. Sections 62 and 68 are joinedby bolts or fastener 70 or other functional means. Crankshaft cradle 60is rotatably supported in housing 59 by eccentric main cap 71. Removablemain cap 71 enables crankshaft cradle 60 to be laid into the housing asan alternative to the slide-in assembly described above. Specifically,FIG. 1 shows a rigid engine construction having a housing 24 having anupper housing portion 24 a and a lower structure 24 b, where the upperhousing portion 24 a and the lower structure 24 b is a one-piece metalcasting, and eccentric members 48 and 50 slide into housing 24 on axisE. Bore 46 may be formed in lower structure 24 b, or lower structure 24b may support a bearing element having a bore 46 for supporting thecradle (not shown). Referring now to FIG. 11, an oil feed line 65 insection 62 and an oil supply galley 67 provide oil to crankshaftbearings 66. Galley 67 is preferably about as wide as it is deep.Referring now to FIGS. 3 and 5, oil feed line 77 is in webbing 64 andoil feed line 65 is in eccentric member 62.

FIG. 4 shows a detailed view of cradle or crankshaft cradle 60.Crankshaft cradle 60 has eccentric members or sections 62 for rigidlysupporting crankshaft bearings 66. Eccentric members or sections 62 arerigidly joined or connected to one another by cross webbing structure64. Referring now to FIGS. 1 and 2, eccentric members or sections 48 and50 are rigidly joined or connected to one another by cross webbing 52and 54. According to the present invention, crankshaft cradle 36includes cross webbing structure 52 and 54 effective for rigidly holdingcrankshaft main bearings 12 in alignment, and crankshaft cradle 60includes cross webbing structure 64 effective for rigidly holdingcrankshaft main bearings 66 in alignment.

Referring now to FIGS. 3, 4 and 11, cross webbing structure 64 has anouter surface 69 a that bears on a bore surface in housing 59 includingan inner housing surface 69 b and on an inner main cap surface 69 c.Crankshaft cradle 60 having outer surface 69 a is rotatably mountedinside said bore surface in housing 59 and/or eccentric main cap 71.Outer surface 69 a may extend onto the outer surface of webbingstructure 64, and outer surface 69 a may form a continuous surfacebetween adjacent eccentric members or sections 62 (shown). According tothe present invention, crankshaft cradle 60 may be supported along allor a portion of bearing surface 69 a.

FIG. 8 shows a partial sectional view of an engine 136 according to thepresent invention. FIG. 8 is similar to FIG. 1 except that FIG. 8 showsa piston type hydraulic actuator 138 having a hydraulic piston 140slidably housed in a hydraulic cylinder 142 for linear translationmovement. Piston 140 is pivotaly connected to an actuator link or arm144, and arm 144 is pivotaly connected to a crankshaft cradle 146.Piston 140 may be connected to cradle 146 by actuator link or arm 144 orby another type of coupling such as a rack and pinion gear set, aneccentric bushing between arm 144 and bolt or pin 164, or anotherfunctional arrangement. Fluid enters and exits cylinder 142 through oneor more passageways 148, and flow of fluid into and out of cylinder 142is controlled by one or more valves (not shown). According to thepresent invention, pressurized fluid entering cylinder 142 throughpassageway 148 forces piston 140 and arm 144 in a generally downwarddirection (with respect to the orientation of engine 136 shown in FIG.8) causing crankshaft cradle 146 to rotate counterclockwise about axis Ecausing crankshaft centerline A to rise and the compression ratio ofengine 136 to be increased.

An actuator first adjusts the rotational position of the crankshaftcradle about its pivot axis E, and then locks the rotational position ofthe cradle in place. Referring now to FIGS. 2, 5 and 9, according to thepresent invention, the actuator is preferably connected to the middle ofthe crankshaft cradle, e.g., between the front and the back mainbearings (e.g., between the two main bearings that are spaced farthestapart) and more generally between the front and back eccentric membersor main bearing supports (e.g., between the two eccentric members thatare spaced farthest apart), providing a centrally applied force on thecradle, whereby twisting of the crankshaft cradle and misalignment ofthe main bearings is minimized. FIG. 9 shows placement of actuator arm144 between the main bearings 12 and more generally between eccentricmembers 160 and 162, providing balanced loading of actuator force oncrankshaft cradle 146. FIG. 5 shows placement of actuator arm 144between the main bearings 66 and more generally between the twoeccentric members 62 spaced farthest apart, providing balanced loadingof actuator force on crankshaft cradle 61. FIG. 2 shows the fluidchamber of an actuator 42 applying even pressure on crankshaft cradle 36along its length, and more generally between eccentric members 48 and50. Accordingly, the eccentric members are rigidly maintained inalignment providing a long main bearing life.

FIG. 9 shows a partial sectional view of engine 136 taken along cutlines F9—F9 shown in FIG. 8. Referring now to FIGS. 8 and 9, engine 136has a housing 150, a piston 4, a connecting rod 6, a crankshaft 152mounted in bearings 12 having an inner diameter 154 for carryingcrankshaft 152, and bearings 12 are housed in crankshaft cradle 146.Hydraulic cylinder 142 is formed in or rigidly aligned with housing 150.Connecting rod 6 has a big-end bearing 156, and is rotatably mounted oncrankshaft 152 on crank 158 having a bearing axis B. Preferablycrankshaft cradle 146 has a first eccentric section 160 and a secondeccentric section 162 that slide onto opposite ends of crankshaft 152,and are rigidly held together by one or more fasteners such as bolts 164and 166, or by other means such as a pin or screw. Section 160 includesa first structure 168 for retaining bolts 164 and 166, and section 162includes a second structure 170 for retaining bolts 164 and 166. Bolt164 may serve as a connecting pin, linking or pivotaly connecting arm144 and crankshaft cradle 146. Preferably, bolt 164 serves as aconnecting pin and is generally centered between section 160 and section162, so that force from arm 144 is substantially applied equally tosections 160 and 162 in order to minimize misalignment of bearings 12.In detail, the connecting pin portion of bolt 164 is located in theaxial direction along axis E between sections 160 and 162, and islocated in the radial direction outside the swept path of crankshaft152, connecting rod 6 (including the connecting rod big end bearingcap), and counterweights (172 shown in FIG. 9). Crankshaft 152 may havecounterweights 172. In FIG. 8, counterweights 172 are not shown (i.e.cut away) to show bearing 156 at the big end of rod 6, and thecrankshaft main bearings 12. As shown in FIG. 9, a pre-tensioning meansin the form of a spring 106 applies a torque on crankshaft cradle 146.Spring 106 may be attached directly to crankshaft cradle 146 and housing150. Preferably, spring 106 is coiled around axis E and attached to anend of crankshaft cradle 146. Referring now to FIGS. 8 and 9, spring 106exerts a clockwise torque on crankshaft cradle 146, and encourages orcauses the compression ratio of engine 136 to be decreased, and morespecifically spring 106 exerts a torque on crankshaft cradle 146 causing(or encouraging) crankshaft cradle 146 to rotate causing crankshaft 152to move in a direction away from piston 4 (e.g., causing or encouragingthe compression ratio of engine 136 to be reduced). Hydraulic pressurein cylinder 142 acts against (e.g., resists) the torque on crankshaftcradle 146 from spring 106, and encourages or causes the compressionratio of engine 136 to be increased.

Oil is fed to bearings 12 and 156 through an oil supply fitting 176preferably located on axis E and having an oil feed passageway 178, thatis in fluid communication with oil feed lines (e.g., crankshaftpassageways) 180 and 182. Preferably oil feed line 180 is located orcentered on axis A, supply fitting 176 is located or centered on axis E,and supply fitting 176 is attached directly to section 160. An off-setpassageway or eccentric transition space 184 connects feed line 180 andoil feed passageway 178 in fitting 176. Supply fitting 176 may include arotary fitting or joint so that oil feed passageway 178 may remainstationary when section 160 and crankshaft cradle 146 rotate. Duringoperation of the present invention, oil enters passageway 178 and flowsinto off-set passageway 184. The oil then flows to bearings 12 and 156through passageways 180, branch passageway 186. and 182. Those skilledin the art will appreciate that other fluid passageway arrangements maybe used according to the present invention to deliver oil to bearings 12and 156. Surfaces 188 and 190 may be lubricated by feed line 192 and/or194.

Gear 14 may have a helical or bevel tooth pattern 196 that pushescrankshaft cradle 146 in the direction of fitting 176. Crankshaft cradle146 may have or bear on a thrust bearing 198 that resists axial thrustexerted by gear 14 or other axial thrust forces from other sources.Those skilled in the art will appreciate that other types of thrustbearings may be used according to the present invention.

Gear teeth 196 bearing down on power shaft gear 18 result in areactionary upward force on gear 14 and crankshaft 152. The presentinvention includes a ridged crankshaft cradle 146 and a stiff housing150 to prevent crankshaft cradle 146 from twisting under these and otherforces and loads.

The crankshaft cradle K63 may be fabricated in cast iron, steel,aluminum, magnesium, titanium, or another material or combination ofmaterials to provide ridged support of the crankshaft main bearings.Axis B and axis A are separated by length L. The stroke of the crankthrow is 2L. The stroke of engine 136 is approximately 2L, and variesslightly because the cylinder axis does not intersect the crankshaftaxis for all compression ratio settings. In general, the stroke ofengine 136 is assumed to be 2L, with minor variances in stroke lengthignored.

Referring now to FIGS. 7 and 12, during the operation of the engine, themovement of the connecting rod defines a connecting rod swept path. Thewebbing and eccentric members are located entirely outside theconnecting rod swept path to prevent mechanical interference. Accordingto the present invention, the engine may have a clearance zone tominimize crankshaft cradle mass and/or to provide clearance around abalance shaft 200 and/or the power shaft 5. In detail, according to thepresent invention, each piston has a translation axis, and the enginehas a mean translation axis or centerline axis 92, where the centerlineaxis is defined as the translation axis in single cylinder engines, andthe bisecting or average translation axis in multi-cylinder V or Wengines. Engine 258 has a cradle 260, webbing 262, a first plane 90originating at pivot axis E and passing through centerline axis 92, thefirst plane and the centerline axis being perpendicular. The engine hasa second plane 250 originating at pivot axis E, the second plane beingseparated from the first plane 90 by 20 degrees, and the engine has athird plane 252 originating at pivot axis E, the third plane and thefirst plane being separated by 20 degrees, and said second plane 250 andsaid third plane 252 being separated by 40 degrees. The connecting rodswept path is bound by a fourth plane 254 and a fifth plane 256 (seeFIG. 9), said fourth and said fifth planes being perpendicular to therotational axis of the crankshaft. Engine 258 has a clearance zone boundby the second plane 250 and the third plane 252 and by the fourth plane254 and the fifth plane 256, and the webbing 262 is located exclusivelyoutside of said clearance zone at all compression ratio settings,providing a mechanical clearance between the crankshaft cradle andbalance shaft 200, power shaft 5, and/or other engine components.

Referring now to FIG. 9, to provide ridged support of crankshaftbearings 12, crankshaft cradle 146 has a maximum thickness t between afirst circle or cylinder 147 and a second circle or cylinder 149. Thefirst circle 147 has a center on the rotational axis of the crankshaft Aand has a diameter of 1.2 times the stroke of the crank throw, and thesecond circle 149 has a center on the rotational axis of the crankshaftA and has a diameter of 2.0 times the stroke of the crank throw.Preferably, the maximum thickness between the first and second circle isat least 0.10 times the thickness of the stroke of the crank throwproviding a rigid cradle. Preferably, the maximum thickness along thefirst circle is also at least 0.10 times the length of the stroke of thecrank throw. According to the present invention, the ratio of thethickest section t of crankshaft cradle 146, between circles 147 and149, divided by length L is greater than 0.10, (e.g., t/L>0.10)providing ridged support of main bearings 12.

Similarly, the crankshaft cradle has a second maximum thickness t2 on aplane 151 perpendicular to the rotational axis A of the crankshaft andpassing through the crank throw 158. The second maximum thickness t2 isat least 0.10 times the length of said stroke providing a rigid cradle(e.g., t2/L>0.10)

As stated before, the crankshaft cradle may be a one-piece cast part, oran assembly of parts. Preferably, the webbing has a first portion, andthe first portion has a thickness at a radial distance from therotational axis of the crankshaft greater than the stroke, wherein afirst eccentric member and the first portion is a one-piece metalcasting, providing a rigid structure between the eccentric member andthe webbing used to join adjacent eccentric members.

To provide low mechanical forces on the cradle, and a high vibrationalnatural frequency of the cradle (higher than the maximum operationalspeed of the engine), preferably the distance between the pivot axis andthe crankshaft axis is at a minimum. Specifically, preferably the pivotaxis passes through the swept path of the connecting rod.

In any event, crankshaft cradle 146 provides ridged support of bearings12, and more specifically crankshaft cradle 146 holds bearings 12 inalignment within a tight tolerance, where the tight tolerance is smallenough to prevent failure of bearings 12 or failure of crankshaft 152.In engines according to the present invention having two or more mainbearing supports, and preferably engines with journal hearings accordingto the present invention, the tight tolerance is preferably a radialdeflection of less than 0.008 inches (and preferably less than 0.004inches) of the centerline of any one bearing 12 from the centerline ofcrankshaft cradle 146, and more specifically, measured from a zerodeflection baseline where crankshaft bearings 12 are on a first straightaxis of rotation and the crankshaft is on a second straight axis ofrotation that is concentric with the first axis of rotation. Thoseskilled in the art will appreciate that the present invention provides atight tolerance for crankshaft cradles that support crankshafts for oneor more cylinder engines. In vehicles (such as in light duty passengercars and light trucks as defined by the U.S. Environmental ProtectionAgency) applications of the present invention, crankshaft cradle 146 hasa rigidity great enough to prevent failure of bearings 12 within aminimum of 100,000 miles of vehicle use. Light duty passenger car andtruck engines are operated at part load most of the time. According tothe present invention, bearing alignment is measured at a first enginesetting having a crankshaft rotational speed between 1200 rotations perminute (rpm) and 6000 rpm, and at an engine mean effective pressure(mep) of less than 500 kilopascals ( 500 kPa). Mean effective pressureis defined on page 50 of Internal Combustion Engine Fundamentals, John,B. Heywood, McGraw-Hill Book Company, 1988, as follows,

mep(kPa)=P(kW)n _(R)×10³ /V _(d)(dm³)N(rev/s)

n_(R) is equal to two (2) for four-stroke engines and one (1) fortwo-stroke engines. V_(d) is swept engine displacement. N is enginerotational speed in revolutions per second, and P is power in kilowatts.More specifically, the first bearing has a first centerline axis and thesecond bearing has a second centerline axis, and the crankshaft cradlehas sufficient rigidity to maintain the first and the second centerlineaxes within 0.008 inches of one another during operation of the engineat the first engine setting.

Engines having no more than two main bearing supports require lessprecise alignment of the main bearings, because a small amount ofbearing misalignment does not apply a bending moment along the length ofthe crankshaft (i.e., a straight crankshaft axis can, in some cases, liebetween two miss aligned bearing supports, but not between three missaligned bearing supports). According to the present invention, forengines having no more than two crankshaft main bearing supports, thecrankshaft cradle has sufficient rigidity to maintain said first andsecond centerline axes within 0.040 inches of one another duringoperation of the engine at said first engine setting. The engine isconsidered to have two crankshaft bearing supports if the two bearingsupports support more than 85 percent of the crankshaft's radial load.Similarly, the crankshaft cradle has sufficient rigidity to limitrotation of the first bearing support or eccentric member relative tothe second bearing support or eccentric member about the pivot axis ofthe cradle to one rotational degree (1°) about pivot axis E at saidfirst engine setting. Crankshaft cradles having roller bearings, such asball bearings, also require less precise alignment of the eccentric mainbearing supports.

Referring now to FIGS. 8 and 9, crankshaft cradle 146 has a lowrotational inertia, enabling actuator 138 to rapidly rotate crankshaftcradle 146 about axis E and to rapidly adjust the position of crankshaftcenterline axis A. Eccentric section 160 has an outer or bearingdiameter 202 that is rotatably housed in a bore 204 in housing 150, andeccentric section 162 has an outer or bearing diameter 190 that isrotatably housed in a bore 188 in housing 150. According to anembodiment of the present invention, to provide a low rotational inertiaand a fast response, the ratio of inner diameter 154 to outer diameter202 is greater than 0.40, and preferably greater than 0.30. Innerbearing diameter 154 refers to the effective diameter and morespecifically the diameter of the hydraulic film separating the crankthrow from the journal bearing element 12. For crankshaft cradles havingroller bearings supporting the radial loads of the crankshaft, such asball, cylindrical (including needle), tapered, and spherical rollerbearings, the effective diameter is the circular path of the individualaxes of rotation of the rolling elements. In the case of tapered,spherical, multiple row bearings, and other roller bearings having arange of circular path diameters, the circular path is measured from thelargest circular path of the individual axes of rotation of the rollingelements. (Dampers, such as dampers 210 and 212, may be used to dampendeceleration of crankshaft cradle 214, shown in FIG. 10.)

FIG. 10 shows a partial sectional view of an engine 216 according to thepresent invention. FIG. 10 is similar to FIG. 8 except that FIG. 10shows a second hydraulic actuator 218 having a piston 220 slidablyhoused in cylinder 222. Piston 220 is pivotally connected to an arm 224,and arm 224 is pivotaly connected to a crankshaft cradle 214. Cylinder222 has a fluid line 226, in fluid communication with a first valve 228and a second valve 230. Second valve 230 may include a first check valve232. Check valve 232 is in fluid communication with a pressurized oilfeed line 234 which receives oil under pressure from the oil pump of theengine. Cylinder 142 has a fluid line 236, in fluid communication with athird valve 238 and a fourth valve 240. Fourth valve 240 may include asecond check valve 242. Check valve 242 is in fluid communication with apressurized oil feed line 244 which receives oil under pressure from theoil pump of the engine. Oil passing through valves 228 and 238 returnsto the engine sump for eventual recirculation by the pump of the oilpump of the engine.

According to the present invention, crankshaft cradle 214 is rotatedcounterclockwise and crankshaft centerline axis A is moved towardspiston 4 by opening first valve 228, opening fourth valve 240, closingsecond valve 230, and closing third valve 238. The position ofcrankshaft cradle 214 and crankshaft centerline axis A is retained in afixed or near fixed position by closing first valve 228, leaving closedsecond valve 230 (optional), leaving closed valve third valve 238, andleaving open valve 240. Pressurized oil flows into cylinder 142 throughfeed line 244, check valve 242, fourth valve 240, and fluid line 236,causing crankshaft cradle 214 to rotate counterclockwise and piston 220to compress oil retained in cylinder 222, where the position ofcrankshaft cradle 214 becomes fixed or nearly fixed when the pressurizedoil entering cylinder 142 through feed line 236 can no longer rotatecrankshaft cradle 214 counterclockwise due to the pressure of the oil incylinder 222, and check valve 242 substantially prevents crankshaftcradle 214 from rotating clockwise. According to the present inventioncrankshaft cradle 214 is rotated clockwise, and crankshaft centerlineaxis A is moved away from piston 4 by closing first valve 228, closingfourth valve 240, opening second valve 230, and opening third valve 238.The position of crankshaft cradle 214 and crankshaft centerline axis Ais retained in a fixed or near fixed position as described above, or byleaving closed first valve 228, leaving closed fourth valve 240, andclosing third valve 238. Those skilled in the art will appreciate thatthe valve opening and closing sequences used to adjust and fix theposition of crankshaft cradle 214 in engine 216, may be used to adjustthe position of crankshaft cradle 112 shown in FIG. 7. Other valveopening and closing sequences may be used to adjust and fix the positionof crankshaft cradle 214 in engine 216, and other types of valves may beused to control flow of fluid into and out of cylinders 142 and 222according to the present invention. The position of crankshaft cradle214 and crankshaft centerline axis A may also be retained in a fixed ornear fixed position by closing first valve 228 opening second valve 230,closing valve third valve 238, and opening fourth valve 240.

Referring now to FIG. 10 (the embodiment shown in FIG. 7 may be operatedin a similar manner), according to the present invention feed lines 244and 234 are pressurized. Preferably standard oil pressure from engine216 (e.g., below 100 psi.) may be used to rotate crankshaft cradle 214and adjust the position of crankshaft centerline axis A. According tothe present invention, the reversing loads on crankshaft cradle 214 fromthe reciprocating motion of piston 4 and connecting arm 6 may be used torotate crankshaft cradle 214 counterclockwise about axis E and movecrankshaft centerline axis A in a direction generally towards piston 4,and in some embodiments of the present invention making possibleoperation of the present invention with small diameter hydraulic pistons140 and 220, and standard or near standard oil pressure. According tothe present invention, the piston and connecting rod exert forces thatchange in magnitude on the crankshaft cradle during the induction andpower strokes of the engine, and the check valve admits and retainsfluid in the actuator during the induction stroke of the piston, causingthe compression ratio to ratchet up. Specifically, crankshaft cradle 214is rotated counterclockwise about axis E and crankshaft centerline axisA is moved in a direction generally towards piston 4 by closing valve230, opening valve 228, closing valve 238, and opening valve 240. Duringthe intake or induction stroke of engine 216, the downward motion ofpiston 4 and connecting rod 6 causes crankshaft 152 to exert an upwardsforce on crankshaft cradle 214, causing crankshaft cradle 214 to rotatecounterclockwise, and fluid to flow out of cylinder 222 through valve228, and fluid to flow into cylinder 142 through valve 240. Check valve242 prevents fluid from leaving cylinder 142 during the power stroke ofpiston 4 when the force on crankshaft cradle 214 and crankshaft 152 frompiston 4 and connecting rod 6 reverses and encourages crankshaft cradle214 to rotate in a clockwise direction about axis E. Accordingly, theposition of crankshaft centerline axis A ratchets up in steps, moving ina direction generally towards piston 4. When a desired position ofcrankshaft centerline axis A is reached, crankshaft cradle 214 may beretained in position by closing valve 228 (and optionally opening valve230). The embodiments of the present invention just described work bestwith engines where the forces on crankshaft 152 reverse direction, suchas in single cylinder engines and some multi cylinder engines, however,the forces on crankshaft 152 do not have to reverse for the rotationalposition of the crankshaft cradle to be adjusted according to thepresent invention, as the oil pressure in feed line 244 will encouragecrankshaft cradle 214 to rotate in a counterclockwise direction when thepressure in cylinder 142 falls below the pressure in feed line 244.Preferably, pressure in line 244 is greater than in cylinder 142 whencrankshaft cradle 214 is rotating counterclockwise, to support rotationof crankshaft cradle 214 and to prevent cavitation of oil in cylinder142. Moving crankshaft centerline axis A in a direction generally awayfrom piston 4 may be accomplished by closing valve 240, opening valve238, closing valve 228, and opening valve 230.

Referring now to FIG. 12. preferably the first hydraulic piston 264 hasthe same area as the second piston 266, and fluid from the firsthydraulic cylinder is directed directly into the second hydrauliccylinder, thereby preventing cavitation.

What is claimed is:
 1. A variable compression ratio mechanism for anengine having at least one cylinder, a piston mounted for reciprocatingmovement in the cylinder, a crankshaft defining an axis about which thecrankshaft rotates, and a connecting rod connecting the piston to thecrankshaft, comprising; a rigid crankshaft cradle supporting thecrankshaft for rotation of the crankshaft about the rotational axis ofthe crankshaft, the cradle being mounted in the engine for pivotingrelative to the engine about a pivot axis, the pivot axis beingsubstantially parallel to and spaced from the rotational axis of thecrankshaft, an actuator for varying the position of the cradle about thepivot axis for varying the position of the rotational axis of thecrankshaft, said cradle comprising a primary member and a plurality ofbearing caps and bearing cap bolts, said primary member comprisingeccentric main bearing supports, said eccentric main bearing supportsbeing rigidly connected by webbing, each bearing cap being removablyfastened to each of said eccentric main bearing supports by said bolts,and a plurality of crankshaft main bearings, said crankshaft mainbearings being mounted between said eccentric main bearing supports andattached bearing caps for rigidly supporting said crankshaft in saidcradle, said engine having a housing for rotatably supporting saidcradle, wherein said webbing rigidly joins said eccentric members, andsaid housing slidably supports each of said bearing caps and saidprimary member thereby providing rigid support of said crankshaft mainbearings.
 2. The variable compression ratio mechanism of claim 1,wherein said primary member is a one-piece metal casting.
 3. Thevariable compression ratio mechanism of claim 2, wherein all of saidcrankshaft main bearings are mounted between said eccentric members andsaid removable bearing camps.
 4. The variable compression ratiomechanism of claim 1, wherein said engine has a crankshaft rotationalspeed, a mean effective pressure, and a first engine setting having arotational speed between 1200 and 6000 rotations per minute and a meaneffective pressure less than 500 kilopascals, said cradle comprises twoor more bearings supporting the crankshaft, said bearings including afirst bearing having a first centerline axis and a second bearing havinga second centerline axis, wherein said first centerline and said secondcenterline are no. more than 0.008 inches apart from one another duringoperation of said engine at said first engine setting.
 5. The variablecompression ratio mechanism of claim 3, wherein said connecting rod hasa swept path and said pivot axis passes through said swept path.
 6. Thevariable compression ratio mechanism of claim 1, wherein said bearingsinclude a first bearing mounted on a first bearing support on saidcradle, said first bearing has an effective diameter and said firstbearing support has an outer diameter, said cradle being pivotallysupported on said outer diameter, wherein the ratio of said firstbearing effective diameter to said first bearing support outer diameteris at least 0.30 thereby providing a rigid cradle having a small inertiaand a fast response.
 7. The variable compression ratio mechanism ofclaim 3, wherein each bearing caps is attached exclusively to oneeccentric member, said bearing caps not being joined to one another,thereby providing clearance for the swept path of the crankshaft.
 8. Thevariable compression ratio mechanism of claim 3, comprising at least twoof said cylinders, at least three eccentric members, and at least threeof said bearings, wherein said webbing rigidly connects said eccentricmembers to one another.
 9. The variable compression ratio mechanism ofclaim 3, wherein, during the operation of the engine, the movement ofthe connecting rod defines a connecting rod swept path, said webbingbeing entirely outside said connecting rod swept path.
 10. The variablecompression ratio mechanism of claim 9, wherein said engine has one ormore pistons each having a translation axis, a centerline axis for theone or more translation axes, a first plane originating at said pivotaxis and passing through said centerline axis, said first plane and saidcenterline axis being perpendicular, a second plane originating at saidpivot axis, said second plane being separated from said first plane by20 degrees, and a third plane originating at said pivot axis, said thirdplane and said first plane being separated by 20 degrees, and saidsecond plane and said third plane being separated by 40 degrees, saidconnecting rod swept path being bound by a fourth and a fifth plane,said fourth and said fifth planes being perpendicular to the rotationalaxis of the crankshaft, a clearance zone bound by the second plane andthe third plane and by the fourth plane and the fifth plane, whereinsaid webbing is located entirely outside of said clearance zone, wherebysaid cradle has a mechanical clearance, a low inertia, and a fastresponse.
 11. The variable compression ratio mechanism of claim 3,wherein said crankshaft has a crank throw having a stroke, and saidcradle has a maximum thickness between a first circle and a secondcircle, said first circle having a center on the rotational axis of thecrankshaft and having a diameter of 1.2 times said stroke, said secondcircle having a center on the rotational axis of the crankshaft andhaving a diameter of 2.0 times said stroke, said maximum thickness is atleast 0.10 times the length of said stroke thereby providing a rigidcradle.
 12. The variable compression ratio mechanism of claim 3, whereinsaid crankshaft has a crank throw having a stroke, and said cradle has amaximum thickness on a plane perpendicular to the rotational axis of thecrankshaft and passing through the crank throw, said maximum thicknessis at least 0.10 times the length of said stroke thereby providing arigid cradle.
 13. The variable compression ratio mechanism of claim 1,wherein said engine has a crankshaft rotational speed, a mean effectivepressure, and a first engine setting having a rotational speed between1200 and 6000 rotations per minute and a mean effective pressure lessthan 500 kilopascals, said cradle comprises no more than two bearingssupporting the crankshaft, said bearings including a first bearinghaving a first centerline axis and a second bearing having a secondcenterline axis, wherein said first centerline and said secondcenterline are no more than 0.040 inches apart from one another duringoperation of said engine at said first engine setting.
 14. The variablecompression ratio mechanism of claim 13, wherein said bearings arerolling element bearings.
 15. The variable compression ratio mechanismof claim 1, wherein said engine has a crankshaft rotational speed, amean effective pressure, and a first engine setting having a rotationalspeed between 1200 and 6000 rotations per minute and a mean effectivepressure less than 500 kilopascals, said bearings include a firstbearing mounted on a first bearing support on said cradle and a secondbearing mounted on a second bearing support on said cradle, wherein saidfirst bearing support is twisted about said pivot axis relative to saidsecond bearing support by no more than one degree of rotation at saidfirst engine setting.
 16. The variable compression ratio mechanism ofclaim 1, wherein said cradle has an outer surface, said actuatorcomprises a hydraulic working fluid, and said hydraulic fluid acts onsaid outer surface.
 17. The variable compression ratio mechanism ofclaim 2, wherein said cradle further comprises an oil feed line havingan oil inlet, a first main bearing and a second main bearing, whereinsaid oil inlet is in fluid communication with said first main bearingand said second main bearing through said oil feed line, and said oilfeed line is located in said webbing between said eccentric main bearingsupports.
 18. The variable compression ratio mechanism of claim 17,wherein said oil feed inlet is located on said pivot axis.
 19. Thevariable compression ratio mechanism of claim 1, wherein said cradlefurther comprises an oil feed line having an inlet, and a plurality ofmain bearings in fluid communication with said oil feed line, whereinsaid oil feed inlet is located on said pivot axis.
 20. The variablecompression ratio mechanism of claim 1, further comprising locking meansfor retaining the cradle in a fixed rotational position, said lockingmeans comprises a first hydraulic actuator for exerting a clockwisemoment on the cradle about the pivot axis, and a second hydraulicactuator for exerting a counterclockwise moment on the cradle about thepivot axis, a hydraulic working fluid, and a check valve for admittingand retaining said working fluid in said first hydraulic actuator. 21.The variable compression ratio mechanism of claim 1, further comprisinglocking means for retaining the cradle in a fixed rotational position,said locking means comprises a first hydraulic actuator for preventingclockwise rotation of the cradle, and a second hydraulic actuator forpreventing counterclockwise rotation of the cradle.
 22. The variablecompression ratio mechanism of claim 21, further comprising a checkvalve for admitting hydraulic fluid into said first hydraulic actuatorfor reducing the rotational play of the cradle about the pivot axis. 23.The variable compression ratio mechanism of claim 21, wherein said firsthydraulic actuator and said second hydraulic actuator are rotaryactuators having a common axis of rotation.
 24. A variable compressionratio mechanism for an engine having at least one cylinder, a pistonmounted for reciprocating movement in the cylinder, a crankshaftdefining an axis about which the crankshaft rotates, and a connectingthe piston to the crankshaft, comprising; a rigid crankshaft cradlesupporting the crankshaft for rotation of the crankshaft about therotational axis of the crankshaft, the cradle being mounted in theengine for pivoting relative to the engine about a pivot axis, the pivotaxis being substantially parallel to and spaced from the rotational axisof the crankshaft, an actuator for varying the position of the cradleabout the pivot axis for varying the position of the rotational axis ofthe crankshaft, said cradle comprising a first eccentric member and asecond eccentric member, and first eccentric member having a first mainbearing mounted on said rotational axis, and said second eccentricmember having a second main bearing mounted on said rotational axis, anda fastener for rigidly connecting said first eccentric member and secondeccentric members to one another, said first eccentric member furtherincluding a first main bearing bore for retaining a first crankshaftmain bearing, said main bearing bore being located in a singlecontiguous portion of said first eccentric member, wherein said singlecontiguous portion fully surrounds said main bearing bore, wherein saidfirst main bearing is spaced apart from said second main bearing alongthe rotational axis of the crankshaft, and said first eccentric memberis spaced apart from said second eccentric member along the rotationalaxis of the crankshaft.
 25. The variable compression ratio mechanism ofclaim 24, wherein said actuator comprises a connecting rod and saidfastener includes a connecting rod journal, said journal connecting saidconnecting rod and said cradle.
 26. The variable compression ratiomechanism of claim 24, wherein said cradle has an outer surface, saidactuator comprises a hydraulic working fluid, and said hydraulic fluidacts on said outer surface.
 27. A variable compression ratio mechanismhaving a housing, at least one cylinder, a piston mounted forreiprocating movement in the cylinder, a crankshaft defining an axisabout which the crankshaft rotates, and a connecting rod connecting thepiston to the crankshaft, comprising: a rigid cradle supporting thecrankshaft for rotation of the crankshaft about the rotational axis ofthe crankshaft, the cradle being mounted in the housing for pivotingrelative to the housing an arcuate distance about a pivot axis beingsubstantially parallel to and spaced from the rotational axis of thecrankshaft; said cradle comprises a first eccentric member, a secondeccentric member, and webbing rigidly connecting said first and secondeccentric members to one another; said connecting rod defining aconnecting rod swept path, said webbing being entirely outside saidconnecting rod swept path; bearings supporting the crankshaft forrotation, said bearings being mounted on said cradle; and an actuatorfor varying the position of the cradle about the pivot axis, whereby therotational axis of the crankshaft is rotated about the pivot axis of thecradle said arcuate distance and the compression ratio is varied.
 28. Apowering output coupling for a variable compression ratio mechanismhaving a housing, at least two pivotable, eccentric main bearingsupports, a crankshaft, and an actuator for pivoting said main bearingsupports, said main bearing supports being pivotably mounted in saidhousing about a pivot axis, said main bearing supports having a firstpivot position and a second pivot position, said crankshaft beingmounted in said main bearing supports on a crankshaft axis spaced fromand substantially parallel to said pivot axis, said actuator beingoperable to pivot said main bearing supports from said first pivotposition to said second pivot position and for moving said crankshaftaxis from a first axial position to a second axial position, comprisingat least one external power take-off gear on said crankshaft, and apower shaft having an axis of rotation and an external power input gear,wherein said external power take-off gear is engaged with said externalpower input gear, said first axial position has a first distance fromsaid power shaft axis of rotation at said first pivot position of saidbearing supports, said second axial position of said crankshaft axis hasa second distance from said power shaft axis of rotation at said secondpivot position of said bearing supports, and said second distance isgreater than said first distance.
 29. The power output coupling of claim28, further having one or more pistons each having a translation axis, acenterline axis for the one or more translation axes, and one or moreconnecting rods connecting the one or more pistons to the crankshaft; afirst plane passing through said pivot axis and perpendicular to saidcenterline axis, a first crankshaft axis located approximately on saidfirst plane, said centerline axis and said crankshaft axis being on thesame side of said pivot axis, a second plane passing through said firstcrankshaft axis, said second plane and said first plane being separatedby 45°, and a third plane passing through said first crankshaft axis,said third plane and said first plane being separated by 45° and saidsecond plane and said third plane being separated by 90°, wherein saidpower shaft is located between said second plane and said third plane,thereby minimizing the maximum backlash between said external powertake-off gear and said external power input gear.